This invention relates to a door locking mechanism, and more particularly the door locking mechanism which can be shifted among its unlocked, half-locked and complete-locked conditions. In its half-locked condition, the door may open in a limited range but a person is not allowed to go in and out.
One of the prior locking mechanisms of this kind is disclosed in Japanese laid-open utility model No. 59-40455(1984). This mechanism comprises a key body to be secured to the hem of a door, a slide key slidably mounted in the key body, the head of the slide key being protrudable out of the key body toward a door frame so as to be shifted to its half-locked and complete-locked positions, a keeper to be secured to the door frame, and a half-locking arm anchored to said key latch and provided with an opening to receive the head of the slide key.
With this mechanism, by shifting the head of the slide key to its half-locked position, it is received only in the opening of the half-locking arm. In this condition, the door may open but the half-locking arm restricts the opening angle of the door within the length of the arm.
By shifting the head of the slide key to its complete-locked position, it is received in the recess of the door frame as well as in the opening of the half-locking arm. In this condition, the door may not open as the head of the slide key is caught by the door frame.
In this mechanism, the slide key is shifted by rotating a locking knob mounted on the key body. The locking knob is provided with a pair of pins oppositely arranged in a radial direction and protruded inwardly of the key body. A swinging plate is mounted inside the key body and one end of the swinging plate is pivoted on the slide key. The swinging plate is provided with a plurality of inlets at the lower edge thereof to be selectively engaged by the pair of pins of the locking knob. By rotating the locking knob, the pair of pins rotate in the same direction and the swinging plate is swung and moved in the sliding direction of the slide key until the pair of pins engage the other inlets of the swinging plate. Thus, the slide key is shifted among its unlocked, half-locked and complete-locked positions.
With the above described prior mechanism, however, as the swinging plate is utilized to convert and transmit the rotary motion of the locking knob into the sliding movement of the slide key, the length of the key body in the sliding direction of the slide key becomes long. Accordingly, it is impossible to secure the key body on the hem of the door in case the hem of the door is narrow.